This invention relates to improved lifting and towing apparatus for vehicles and in particular relates to lifting and towing apparatus adapted to be mounted beneath the floor at the rear portion of a vehicle. The invention is particularly suited to, although not limited to, light vehicles such as pick-up trucks and various type of recreational and utility vehicles.
The prior art has provided various lifting and towing arrangements which are adapted to be mounted beneath the bed of the truck thus leaving the bed substantially unobstructed for normal useage with the actual working engaging elements of the lift being disposed just rearwardly of the truck bed. An example of one such prior art arrangement is shown in U.S. Pat. No. 3,667,631 issued June 6, 1972 to Bishop. This patent discloses a hydraulic utility lift for pick-up trucks and other vehicles consisting of a frame adapted to be mounted under the rear portion of the truck bed and carrying a lift arm adapted to lift a load disposed rearwardly of the truck as such arm is pivoted from a downwardly and rearwardly inclined position to a substantially horizontal position. A hydraulic ram is provided for pivoting the arm and the linkage operatively connects the ram to the arm. The linkage is arranged such that it converts horizontal movements of the ram to vertical movement lifting the arm so that the arm may be elevated to provide better ground clearance for the lift, an effort also being made in the design to provide a somewhat more uniform power ratio for the ram.
Another form of lifting and towing arrangement mounted, in essence, below the bed of a truck is shown in U.S. Pat. No. 2,715,470 issued Aug. 16, 1955 to Marcus et al. This patent discloses a hydraulically activated platform for lifting and carrying a wrecked car, which platform is also arranged to serve as a tailgate for the truck, the object of the invention being to provide a wreck-lifting device which is alleged not to substantially interfere with the normal use and loading of the truck.
The known prior art devices suffer from a number of disadvantages. One serious disadvantage is that they apply, when in use, a very substantial amount of additional strain to the main frame of the vehicle and, if the loadings are high, substantial damage can occur. In addition, the extra loadings on the vehicle incurred as a result of the weight of the vehicle being towed must be taken up by the main springs of the vehicle with the result being that the vehicle tends to "squat down" or sway under the influence of these loadings. This is most undesirable since it reduces the available ground clearance and may make the tow vehicle unstable. Furthermore, the prior art devices generally tend to reduce the available ground clearance to an unacceptable degree, especially when loaded, and, moreover, such devices do not allow for the use of the normal rear vehicle bumper when in the inactive or retracted mode. Certain of the prior art arrangements are also difficult to attach or remove from the vehicle with the result being that the lift-tow arrangement tends to be left on the vehicle at all times thus in some cases reducing its usefulness for other types of work or, at the least, creating additional weight which must be carried around at all times with a resulting deduction in fuel economy.